docs: error in mec15xxevb assy6853 in set up manual
docs: error in mec15xxevb assy6853 in set up manual

Error in that manual.
Header JP39 should have connected jumpers 1-2, 3-4.
In docs I wrote that is to make sure JP39 does not have any jumper.

Signed-off-by: Maksim Masalski <00762c94550ce68b2a0e3f1373f5a19cd4f4bbbb@intel.com>

nashif/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,galak/zephyr,finikorg/zephyr,nashif/zephyr,finikorg/zephyr,Vudentz/zephyr,Vudentz/zephyr,Vudentz/zephyr,Vudentz/zephyr,galak/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr